Presently there are a variety of pressure vessels developed for use in various applications, such as those designed to contain gases for use in fuel cells. Fuel cells have been proposed as a clean, efficient and environmentally responsible power source for electric vehicles and various other applications. One example of a fuel cell is a Proton Exchange Membrane (PEM) fuel cell. In the PEM type fuel cells, hydrogen is supplied as a fuel to an anode of the fuel cell and oxygen is supplied as an oxidant to a cathode of the fuel cell. Hydrogen is colorless, odorless, burns without producing a visible flame or radiant heat, and is difficult to contain. A common technique for storing hydrogen is in a lightweight, high pressure vessel resistant to punctures.
Traditionally such vessels are divided into four types. A Type I vessel is a metal vessel. A Type II vessel is also a metal vessel, the vessel having an outer composite shell disposed on a cylindrical section thereof. A Type III vessel consists of a liner produced from a metal such as steel and aluminum, for example, and an outer composite shell that encompasses the liner and militates against damage thereto. A Type IV vessel is substantially similar to the Type III vessel, wherein the liner is produced from a plastic. Furthermore, a conceptual Type V vessel may be developed, wherein the vessel is produced from a composite material. Each type of vessel may include at least one boss disposed therein to receive a valve.
Typically, the valve disposed in the boss includes a valve housing having an external groove terminating in an annular flange. The flange is formed on the valve housing adjacent the groove to abut the vessel. An O-ring having an inner surface and an outer surface is seated in the groove of the valve housing to militate against a leakage of fluid from the vessel. The inner surface of the O-ring is adapted to abut the groove to form a substantially fluid-tight seal therebetween. The outer surface is adapted to abut the liner to form a substantially fluid-tight seal therebetween. During operation, an interior of the vessel is subjected to temperatures below a predetermined temperature such as during defueling, for example. The temperatures below the predetermined temperature cause the O-ring to contract radially inwardly onto the valve housing. Accordingly, a passage is formed between the outer surface of the O-ring and the liner, causing the leakage of fluid therethrough.
It would be desirable to produce a seal to militate against a leakage of fluid due to thermal expansion and contraction, wherein the cost thereof is minimized and the durability and reliability thereof are maximized.